1. Field of the Invention
The present invention relates to a method of forming a film, and more particularly to a method of forming a silicone film for use as an interlayer insulation film of a semiconductor device such as of VLSI (Very Large Scale Integration).
2. Description of the Relevant Art
Silicone films which are excellent in insulation, heat resistance, and stability are employed, for example, as orientation films in liquid crystal display devices and as interlayer insulation films of electronic devices such as semiconductors of VLSI. One process which is widely recently used to form such a silicone film is a "coating method" capable of forming a silicone film of relatively high quality in simple operation. According to the coating method, a coating solution for forming a silicone film is coated on a substrate up to a prescribed thickness, and thereafter heated normally at a temperature of 300.degree. C or higher, thus forming a silicone film.
Where a photoresist, or a film formed by CVD or PVD, or another film is directly coated on a silicone film which has been produced by the coating method, the silicone film and the film formed thereon do not sufficiently adhere to each other. To avoid this drawback, before another film is applied to a silicone film, the surface of the silicone film is ground into a rough surface by sandpaper, or the surface of the silicone film is activated by being exposed to a corona discharge or ultraviolet radiation. However, this process of forming a silicone film having a sufficient adhering ability is complex and results in a high cost.
According to Japanese Laid-Open Patent Publication No. 57-111046, the adhesion capability of a silicone film is improved by depositing a layer of SiO.sub.2 or Al.sub.2 O.sub.3 on a film of polysilsesquioxane which is one type of silicone. However, since the step of depositing the layer of SiO.sub.2 or Al.sub.2 O.sub.3 is required, the overall process of forming a desired silicone film is not simplified and reduced in cost.
The present invention has been made in an effort to effectively solve the aforesaid problems of the conventional methods of forming a silicone film suitable for having another film formed thereon.